Variations during fabrication or manufacture of integrated circuit (IC) chips can cause unpredictable and undesired variations of circuit parameters. As a result of these parameter variations, operational circuits implemented on an IC chip may not meet their desired performance characteristics. Conventional techniques use complicated analog correction circuits, such as constant-Gm bias, to adjust for deviations from optimal operation caused by process and temperature variations. Such circuits consume significant power and can typically only correct one parameter at a time. In fact, correcting more than one circuit parameter often results in the subsequent correction circuit undoing what the first correction circuit adjusted. In addition, in the case of analog correction circuitry, no readily usable output is available for the automated tester. Thus, monitoring variations among the large number of chips manufactured is difficult.
Conventional adjustment circuits are typically closed-loop feedback systems. As a result, stability (e.g., oscillation of the circuit) is often an issue. Furthermore, conventional techniques typically use circuits such as reference oscillators or filters that run in parallel with the operational circuit passing the signal. Such oscillators or filters can create spurs that couple onto the signal path, impacting the performance of the compensation circuit.
Accordingly, a need exists for a simple, flexible, open-loop compensation system that can simultaneously adjust multiple parameters associated with an operational circuit.